We used the setal counting system for metanotal and tergal setae as recommended by Valim and Weckstein (2013) and Kolencik et al. (2016), as follows: (1) the number of metanotal setae does not include the most posterolateral setae; (2) the number of tergal setae on tergite I does not include the postspiracular setae; and (3) the numbers of tergal setae on tergites II–VIII neither include the postspiracular setae nor the short associated setae.

Since previous authors (Klockenhoff 1984a, b; Tendeiro 1993; Price and Dalgleish 2007; Palma and Price 2010; Cicchino and Valim 2015) used different setal counting system in their descriptions or redescriptions of species within the “serini species group”, we modified their data according to the aforementioned system. Therefore, to avoid misunderstandings, we urge authors to make careful comparison of Myrsidea descriptions based on the different systems that include the metanotal and tergal setae. In the following descriptions, all measurements are in millimetres. Abbreviations for dimensions are: dhs, dorsal head seta; ls5, labial setae 5; TW, temple width; POW, preocular width; HL, head length at midline; PW, prothorax width; MW, metathorax width; AWIV, abdomen width at level of segment IV; TL, total length; ANW, female anus width; GW, male genitalia width; GL, male genitalia length; ParL, paramere length; GSL, genital sac sclerite length. Additionally, measurements were made for the setae which compose the aster of sternite II; these are presented from the inner seta to the outer most seta (s1, s2, s3, etc). The taxonomy and nomenclature of the birds follow those in Clements et al. (2019).

We were able to examine specimens of M. balati, M. quadrifasciata, M. queleae, M. serini, M. textoris, and M. viduae. For comparison to other species (M. anoxanthi, M. darwini, M. major), we used precise descriptions or redescriptions of these species by Price and Dalgleish (2007), and Palma and Price (2010). The specimens examined are deposited in the following institutions: K.C. Emerson Entomology Museum, Oklahoma State University, Stillwater, Oklahoma, USA (KCEM); Moravian Museum, Brno, Czech Republic (MMBC); Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand (MONZ); Museu Bocage, Museo Zoologico da Universidade de Lisboa, Lisboa, Portugal (MZUL); Natural History Museum, London, U.K. (NHML); Slovak National Museum, Bratislava, Slovakia (SNMB); National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA (USNM); and Zoological Research Museum Alexander Koenig, Bonn, Germany (ZFMK). As we propose synonymy of nine species from the “serini species group” with M. quadrifasciata, we rename this species group as the “M. quadrifasciata complex” and refer to Myrsidea from particular hosts under their previous names in quotation marks, for example, “M. serini”, “M. textoris”, etc. for better orientation and to avoid repetition of lists of hosts of these taxa in the following text (for specification see supplement Table S1).

For statistical analysis, we used the most variable data mentioned by Klockenhoff (1984b) – the number of setae on the metanotum, tergites I–VIII, sternites III–VII and selected measurements – and compared them with our data by t-test (Tables S13–16). Correlation between host body size and louse body size was calculated according to Harnos et al. (2016). Avian body size in centimetres or body mass in grams was expressed as log-transformed body size or body mass obtained from del Hoyo et al. (2018). We use only two measures of louse body size: log-transformed total body length and temple width of adult females. By our experience, temple width is a measurement with the lowest intraspecific variability that is usually not affected by slide mounting.

Principal Component Analyses (PCAs) were run to additionally examine morphological characteristics of male and female lice. The R package ggplot2 (Wickham 2016) for R 4.0.3 (R Core Team, 2016) was used to visualise data. Obtained plots were adapted in INKSCAPE 0.91 (https://inkscape.org/de).

Sequences of a 379 base pair (bp) fragment of the mitochondrial cytochrome c oxidase I gene (COI) were obtained from Myrsidea sp. ex Spinus magellanicus from Peru (A/N KY113129), M. serini ex Agelaioides badius from Paraguay (A/N KY113130), Myrsidea sp. ex Microspingus melanoleucus (A/N MT526017), M. textoris ex Ploceus intermedius and Ploceus velatus from South Africa (A/N KF768813–KF768815), using methods described by Johnson et al. (2002). Purified PCR products were sequenced using both respective primers (L6625 and H7005) by Macrogen Europe (The Netherlands).

Sequences of a 347 bp fragment of the nuclear elongation factor 1-alpha (EF-1α) gene were obtained from Myrsidea sp. ex Spinus magellanicus from Peru (A/N MT515729), M. serini ex Agelaioides badius from Paraguay (A/N MT515731), Myrsidea sp. ex Microspingus melanoleucus (A/N MT515735), and Myrsidea sp. ex Sporophila nigricollis (A/N MT968994) using methods described by Johnson et al. (2002). Purified PCR products were sequenced using both respective primers (EF1-For3 and Cho10) by Macrogen Europe (The Netherlands).

In order to assess the genetic divergence within the M. quadrifasciata complex, uncorrected p-distances from each specimen was obtained for COI and EF-1α sequences, sequences of five species with lowest p-distances of COI obtained by BLASTing our sequences against GenBank (M. cf. bubalornithis Klockenhoff, 1984, M. seminuda Eichler, 1951, M. cf. textoris, Myrsidea sp. ex Vidua macroura, and Myrsidea sp. ex Linurgus olivaceus) and sequences of three species from Ploceidae (M. eisentrauti Klockenhoff, 1982, M. ledgeri Klockenhoff, 1984, and Myrsidea sp. ex Ploceus nigricollis) (see Table 2). Uncorrected p-distances were calculated in Geneious 9.1.8 (Kearse et al. 2012).

In order to evaluate the position of M. quadrifasciata complex within Myrsidea, two phylogenetic analyses were performed: 1) analysis based on the COI gene fragment, and 2) analysis based on concatenated sequences of the COI gene fragment and the EF-1α gene fragment. To build the COI gene tree, we first downloaded all available Myrsidea sequences from the GenBank and subsequently utilized all the full-length sequences (379 bp), which were unique (except for M. nesomimi where only single representatives of each of the subspecies M. nesomimi borealis Palma and Price, 2010 and M. nesomimi nesomimi Palma and Price, 2010 were selected in order to keep the analysis presentable). The final alignment consisted of 186 sequences (including Dennyus hirundinis as an outgroup taxon for rooting) and 387 bp. For a list of utilized sequences, see Table S2 in the Supplementary material.

For the concatenated tree, we downloaded all available Myrsidea sequences from the GenBank database and subsequently included all available samples with both COI and EF-1α sequences. Pairs of sequences for each sample were concatenated and all unique concatenates were subsequently used to build the phylogenetic tree. The final alignment consisted of 64 sequences (including Dennyus hirundinis as an outgroup taxon for rooting) and 675 bp. For a list of utilized sequences, see Table S2 in the supplementary material.

For both phylogenetic analyses, we first used the Akaike information criterion (AIC) computed in MEGA 7.0.14 (Kumar et al. 2016) to identify the most appropriate models of nucleotide substitution for each gene. Both trees were built using the maximum likelihood (ML) method conducted by PhyML 2.2.0 plugin in Geneious 9.1.8 (Guindon and Gascuel 2003; Kearse et al. 2012) with the GTR+G+I model and parameters estimated from the data; nodal supports were generated with 1,000 bootstrap replicates. The resulting trees with the best likelihood scores were chosen. The trees were visualised using TreeGraph 2.12.0 (Stöver and Müller 2010).

Psocodea Hennig, 1966: 187

Phthiraptera Haeckel, 1896: 703

Amblycera Kellogg, 1896a: 68

Menoponidae Mjöberg, 1910: 26

Myrsidea Waterston, 1915: 12

Myrsidea quadrifasciata (Piaget, 1880)

Figs 1–3, 4–18, 19–20

Menopon quadrifasciatum Piaget, 1880: 440, pl. XXXV, fig. 6. Type host: Passer domesticus (Linnaeus, 1758).

Myrsidea quadrifasciata (Piaget, 1880): Thompson (1937), Clay (1949b), Thompson (1957), Touleshkov (1962, 1974), Macháček (1977a), Lakshminarayana (1979), Gadzhiev and Mustafaeva (1981), Price et al. (2003: 131), Mey (2004), Manilla (2000), Saxena et al. (2007), Naz et al. (2021).

Menopon quadrifasciatum var. major Piaget, 1880: 441. Type host: Plectrophenax nivalis (Linnaeus, 1758). New synonymy.

Myrsidea major (Piaget, 1880): Thompson (1937), Clay (1949a), Emerson (1972), Price et al. (2003: 130), Price and Dalgleish (2007: 14).

Menopon argentinus Kellogg, 1906: 49, pl. II, fig. 7. Type host: Spinus magellanicus (Vieillot, 1805). New synonymy.

Myrsidea argentina (Kellogg, 1906): Price et al. (2003: 128), Cicchino and Valim (2015: 241, fig. 34).

Menopon serini Séguy, 1944: 80, fig. 84. Type host: Serinus serinus (Linnaeus, 1766). New synonymy.

Myrsidea serini (Séguy, 1944): Hopkins and Clay (1952: 233), Negru (1963: 11), Negru (1965: 499, fig. 1e), Klockenhoff (1984a: 18, figs 1–4, tables 1–2, 1984b: 283), Price et al. (2003: 131), Price and Dalgleish (2007: 12, fig. 39), Cicchino and Valim (2015: 232, figs 1–33), Kolencik et al. (2016: 245).

Liquidea serini (Séguy, 1944): Złotorzycka (1964: 169, 176).

Myrsidea queleae Tendeiro, 1964: 182, photos 11–16. Type host: Quelea quelea lathami (Smith A., 1836). New synonymy.

Myrsidea queleae Tendeiro, 1964: Klockenhoff (1984b: 281), Price et al. (2003: 131), Sychra et al. (2010), Halajian et al. (2014).

Myrsidea balati Macháček, 1977a: 1, figs 1a, b, 4, 7–8. Type host: Passer montanus (Linnaeus, 1758). New synonymy.

Myrsidea balati Macháček, 1977: Price et al. (2003: 128), Adam (2007), Adam et al. (2009).

Myrsidea textoris Klockenhoff, 1984b: 270, figs 1–3, 10a, 11a, b. Type host: Ploceus cucullatus cucullatus (Müller, 1776). New synonymy.

Myrsidea textoris Klockenhoff, 1984b: Lindholm et al. (1998: 147); Price et al. (2003: 132); Halajian et al. (2012: 65, 2014: 770); Sychra et al. (2014b: 599).

Myrsidea viduae Tendeiro, 1993: 57, figs 2, 4, 6. Type host: Vidua macroura (Pallas, 1764). New synonymy.

Myrsidea viduae Tendeiro, 1993: Price et al. (2003: 133).

Myrsidea anoxanthi Price and Dalgleish, 2007: 13, figs 40–44. Type host: Loxipasser anoxanthus (Gosse, 1847). New synonymy.

Myrsidea darwini Palma and Price, 2010: 136, figs 1–5. Type host: Geospiza fuliginosa Gould, 1837. New synonymy.

Type host

Passer domesticus (Linnaeus, 1758) (Passeridae).

Type locality

Unknown (most likely Netherlands).

Differential diagnosis

In both sexes showing the characteristics of the “M. serini-Artengruppe” (Klockenhoff 1984b), or serini species-group (Price and Dalgleish 2007). It is well characterized with 1) weakly developed hypopharyngeal sclerites; 2) abdominal segments with continous row of tergal setae across segments I–II, and with well-defined median gap in row of tergal setae on other segments; 3) the females with non enlarged and unmodified tergites (except tergites II–III with slight medioposterior curvature) (Figs 1–3); 4) the females with a strongly spiculate posterior margin of the subgenital plate; and 5) the males with characteristic genital sac sclerites (Figs 4–18).

Figures 1–3. 

Dorsal view of female metathorax and abdomen. 1: Myrsidea quadrifasciata quadrifasciata ex Passer domesticus. 2: M. q. quadrifasciata ex Passer montanus. 3: M. q. queleae ex Quelea quelea.

Figures 4–18. 

Male genital sac sclerites of Myrsidea quadrifasciata. 4–5: M. q. quadrifasciata ex Passer domesticus. 6–7: M. q. quadrifasciata ex Passer montanus. 8: M. q. argentina ex Agelaoides badius from Paraguay. 9–11: M. q. argentina according to Cicchino and Valim (2015). 12–13: M. q. serini according to Klockenhoff (1984a). 14: M. q. darwini according to Palma and Price (2010). 15: M. q. anoxanthi according to Price and Dalgleish (2007). 16: M. q. textoris ex Ploceus cucullatus. 17–18: M. q. queleae ex Quelea quelea.

Description

The following overall description is based on a large number of specimens from different hosts. Data for the most important morphometric characteristics for specimens according to their hosts are presented in supplement Tables S3b–S12. For better orientation and to avoid repetition of lists of hosts in the following text we refer to Myrsidea from particular hosts under their previous names in quotation marks, for example, “M. serini”, “M. textoris”, etc. (for specification see Table S1).

To evaluate the status of “M. argentina” we also examined available nymphs of 3rd instar: 1) two nymphs from Spinus magellanicus – type host of “M. argentina”, and 2) one nymph from Passer montanus – host of M. quadrifasciata. These nymphs differ from previous descriptions of “M. argentina” by Kellogg (1906) and “M. serini” by Cicchino and Valim (2015). Here the essential characters are given, with data from Kellogg (1906) and Cicchino and Valim (2015) in parentheses as (Kellogg/Cicchino and Valim).

FEMALE (n=167) (as in Fig. 19): Head. Hypopharyngeal sclerites weakly developed. Length of dhs 10, 0.05–0.10; dhs 11, 0.07–0.11; ratio dhs 10/11, 0.70–1.10. Ls5 0.06–0.07 long, latero-ventral fringe with 9–10 setae. Gula with a total of 7–11 setae (3–6 setae on each side). Thorax. Pronotum with 6 setae on posterior margin and 3 short spiniform setae at each lateral corner. Prosternal plate with rounded anterior margin. First tibia with 3–4 outer ventro-lateral and 3–4 dorsolateral setae. Mesonotum divided. Metanotum not enlarged, with 6–13 marginal setae; metasternal plate with 4–8 setae; metapleurites with 3–4 short strong spiniform setae. Femur III with 14–21 setae in ventral setal brush. Abdomen. Tergites not enlarged, all with straight posterior margin, only tergites II–III slightly convex medioposteriorly. Abdominal segments with continous row of tergal setae across segments I–II, and with small, but noticeable, median gap in row of tergal setae on other segments. Tergal setae: I, 7–18; II, 8–18; III, 7–19; IV, 7–17; V, 6–15; VI, 5–14; VII, 4–11; VIII, 3–8. Postspiracular setae long to extremely long on II, IV, VII and VIII and shorter on I, III, V and VI with length as in Table S9. Inner posterior seta of last tergum as long as or longer than anal fringe setae with length 0.09–0.10; length of short lateral marginal seta of last segment, 0.03–0.05. Pleural setae: I, 2–6; II, 5–8; III, 5–9; IV, 5–8; V, 4–7; VI, 4–6; VII, 3–5; VIII, 2–4. Pleurites I–II with only short spine-like setae; pleurites III–VII also with 1–2 slender and longer setae; without anterior pleural setae. Pleurite VIII with inner setae (0.02–0.03) as long as outer (0.02–0.04). Anterior margin of sternal plate II with a medial notch. Sternal setae: I, 0; II, 3–5 in each aster, aster setae length: s1, 0.09–0.11; s2, 0.05–0.07; s3, 0.04–0.06; s4, 0.03–0.05; with 9–20 marginal setae between asters, 4–14 medioanterior; III, 16–31; IV, 27–45; V, 27–49; VI, 12–39; VII, 11–22; VIII–IX, 6–22; and 6–14 setae on deeply serrated vulval margin; sternites III–VII without medioanterior setae. Anal fringe formed by 27–43 dorsal and ventral setae. Measurements. TW, 0.34–0.46; POW, 0.30–0.34; HL, 0.25–0.32; PW, 0.18–0.30; MW, 0.36–0.51; AWIV, 0.51–0.71; ANW, 0.19–0.24; TL, 1.26–1.80.

Figures 19–20. 

Myrsidea quadrifasciata quadrifasciata ex Passer domesticus. 19: Female. 20: Neotype male.

MALE (n=90) (as in Fig. 20). Similar to female except as follows. Head. Length of dhs 10, 0.05–0.10; dhs 11, 0.06–0.11; ratio dhs 10/11, 0.70–1.10. Ls5 0.05–0.06 long. Thorax. Metanotum not enlarged with 6–14 marginal setae; metasternal plate with 4–6 setae; metapleurites with 3 strong, short spiniform setae. Femur III with 15–20 setae in ventral setal brush. Abdomen. Abdominal segments with continous row of tergal setae at least across segments I–III, with small median gap in row of tergal setae on other segments. Tergal setae: I, 9–18; II, 9–21; III, 9–22; IV, 7–26; V, 9–23; VI, 8–24; VII, 6–19; VIII, 4–14. Length of inner posterior seta of last tergum, 0.07–0.08; short lateral marginal seta of last segment, 0.03. Pleural setae: I, 3–5; II, 5–8; III, 5–9; IV, 5–7; V, 4–8; VI, 3–6; VII, 3–6; VIII, 2–3. Pleurites I–II with only short spine-like setae; pleurites III–VII also with 1–4 slender and longer setae; without anterior pleural setae. Pleurite VIII with inner setae (0.03) as long as outer (0.03–0.04). Sternal setae: I, 0; II, 3–4 in each aster, aster setae length: s1, 0.07–0.08; s2, 0.04–0.06; s3, 0.03–0.04; s4, 0.02; with 8–16 marginal setae between asters, 4–14 medioanterior; III, 16–34; IV, 24–44; V, 24–45; VI, 21–39; VII, 12–24; VIII, 4–19; remainder of plate, 6–8; and with 3–6 setae posteriorly; sternites III–VII without medioanterior setae. With 6–12 internal anal setae. Genital sac sclerite as in Figs 4–18. Measurements. TW, 0.33–0.42; POW, 0.28–0.33; HL, 0.23–0.30; PW, 0.20–0.29; MW, 0.28–0.41; AWIV, 0.37–0.54; GW, 0.09–0.10; GL, 0.34–0.43; ParL, 0.06–0.08; GSL, 0.03; TL, 1.05–1.41.

THIRD INSTAR NYMPH . Marginal seta of metanotum 7 (4/6). Tergocentral setae of abdomen: I, 7–10 (10/8–9); II, 8–9 (11/8); III, 8 (11/8–9); IV, 8 (11/8–9); V, 6–7 (10/6–7); VI, 6 (10/6–7); VII, 5–6 (9/6); VIII, 4–5 (4/4). Number of setae of dorsal anal fringe, 16–21 (cca 15/15). Dimensions: HL, 0.25–0.29 (0.27/0.28–0.30); TW, 0.35–0.36 (0.35/0.39–0.40); TL, 1.20–1.29 (1.20/1.40–1.41).

Material examined

Ex Passer domesticus (Passeridae): 1♂ (designated as a neotype), England: Cheshire, Great Budworth, 5.xii.1934, A.W. Boyd leg. (NHML: B.M.1955–616); 2♂, 2♀, USA: Mississippi, Tibbee, 15.iii.1936, E.W. Stafford leg. (KCEM: 8170, 8172–74); 1♂, 1♀, USA: Hawaii, Honolulu, 8.ii.–8.iii.1947, J. Alicata leg. (USNM: Lot 47-4795, vial 2). — Ex Passer montanus (Passeridae): 1♀ (paratype of M. balati), Czech Republic, Nesyt, 9.xi.1973, P. Macháček leg. (ZFMK: 1986/15), 1♂, Czech Republic, Jinačovice (49°15′N 16°31′E), 13.i.2006, O. Sychra and I. Literak leg. (MMBC), 1♀, Czech Republic, Moravské Knínice (49°17′N 16°29′E), 8.ii.2009, O. Sychra and I. Literak leg. (MMBC), 1♀, Czech Republic, Kardašova Řečice, 19.vii.1938, K. Pfleger leg. (SNMB); 1♀, Hungary, Nagykanizsa, 28.vi.1952, Balát coll. (MMBC: B185), 1♀, Hungary, Bajcza (Zala m.), 19.iv.1953, Balát coll. (MMBC: C579); 1♀, 1 nymph, Slovakia, Gabčíkovo, 22.vii.1953, Balát coll. (MMBC: 1380), 2♂, 1♀, Slovakia, Gbelce (47°51′N 18°30′E), 10.vii.2019, O. Sychra and L. Oslejskova leg.; 3♂, 3♀, Thailand, San Sai, Ban Pong, 16.ii.1962, Kitti Thonglongya leg. (KCEM: 8183–85); 1♀, W. Java, Bogor, 8.xi.1968 (KCEM: 9E 0414); 2♀, no data (NHML: 840). — Ex Agelaius phoeniceus (Linnaeus, 1766) (Icteridae): 9♀, 3♂, USA: South Carolina, Charleston, 1934, 27.iii.1933, H.S. Peters leg. (USNM: Bish. 1934 #20711). — Ex Agelaoides badius badius (Vieillot, 1819) (Icteridae): 1♀, 4♂, Paraguay, Los Tres Gigantes Biological Station in the Pantanal (20°04′S 50°09′W), 6.ix.2012, I. Literak leg. (MMBC: PG357). — Ex Emberiza citrinella caliginosa Clancey, 1940 (Emberizidae): 1♀, 1♂, New Zealand, Raoul I., Kermadec Is., 11.xii.1972; J. Ireland leg., R.L.C. Pilgram Collection (MONZ). — Ex Euplectes franciscanus (Isert, 1789) (Ploceidae): 2♂, 2♀, Senegal, Niokolo Koba National Park, Simenti (13°02′N 13°18′W), 8.ii.2005, P. Prochazka leg. (MMBC). — Ex Euplectes jacksoni (Sharpe, 1891) (Ploceidae): 1♂, 3♀, Kenya, i.1936, Meinertzhagen coll. (NHML: No.6081). — Ex Euplectes orix (Linnaeus, 1758) (Ploceidae): 2♀, South Africa, Pietermaritzburg, Scottsville (29°39′S 30°23′E), 7. and 19.ii.1994, A. Lindholm leg. (slide no. 57A, 106A). — Ex Euplectes progne delamerei (Shelley, 1903) (Ploceidae): 2♂, Kenya, iii.1936, Meinertzhagen coll. (NHML: No.7462); 1♂, 3♀, Kenya, ii.1936, Meinertzhagen coll. (NHML: No.6715). — Ex Foudia madagascariensis (Linnaeus, 1766) (Ploceidae): 1♂, 2♀, Madagascar, Diego Suarez, 1921, G. Melow Coll. (NHML: 1921–200). — Ex Passer luteus (Lichtenstein, M.H.C., 1823) (Passeridae): 3♀, Senegal, Matam (15°37′N 13°20′W), 6.ix.2007, I. Literak and M. Capek leg. (MMBC). — Ex Ploceus cucullatus cucullatus (Statius Müller, 1776) (Ploceidae): 1♂, 3♀, Senegal, Kaolack (14°09′N 16°06′W), 7.ix.2007, I. Literak and M. Capek leg. (MMBC). — Ex Microspingus melanoleucus (d‘Orbigny and Lafresnaye, 1837) (Thraupidae): 1♀, Paraguay, Los Tres Gigantes Biological Station in the Pantanal (20°04′S 50°09′W), 6.ix.2012, I. Literak leg. (MMBC: PG359). — Ex Ploceus cucullatus nigriceps (Layard, 1867) (Ploceidae): 1♂, Mozambique, Zambue, Tete District, 3.ix.1964, A.L.Moore leg. (KCEM: A36). — Ex Ploceus nigricollis brachypterus Swainson, 1837 (Ploceidae): 1♂, 1♀, Cameroon, Yaounde, 1955, J. Mouchet (NHML: B.M.1955–737). — Ex Ploceus philippinus (Linnaeus, 1766) (Ploceidae): 1♂, 5♀, 1 nymph, India, Deccan, ii.1937, Meinertzhagen coll. (NHML: No.8615–17); 2♀, India, Daulatabad, Maharastra, 25.vi.1969, (KCEM: S.No.XE–363, XE–193, AB–24042); 1♀, India, Daulatabad, Aurangabad, 20.vii.1968, (KCEM: 9E 0250, A81348); 1♀, Thailand, Doi Pha Hom Pok Chiengmai 22.xii.1965, (KCEM: MAPS–3658). — Ex Ploceus velatus tahatali A. Smith, 1836 (Ploceidae): 1♂, South Africa, Limpopo province, Polokwane Game Reserve (23°58′S 29°28′E), 11.ii.2012, A. Halajian leg. (MMBC). — Ex Quelia cardinalis (Hartlaub, 1880) (Ploceidae): 1♂ (paratype of M. queleae), Bechuanaland (now Botswana), Mababe, 6.x.1952, F. Zumpt leg. (NHML: B.M. 1959–273). — Ex Quelea quelea aethiopica (Sundevall, 1850) (Ploceidae): 1♂, 1♀, Sudan, May 1936, Meinertzhagen coll. (NHML: No.7836). — Ex Quelea quelea lathami (Ploceidae): 1♂, Southern Rhodesia (now Zimbabwe), Matopos, 30.iii.1952 (NHML: B.M.1980–40, coll.691); 1♂, 1♀, Transvaal (now South Africa), Nr. Komatipoort, 18.i.1961, F. Zumpt leg. (NHML: B.M.1965–526); 4♂, 3♀, South Africa, Limpopo province, De Loskop (23°30′S 29°18′E), 7.xii.2012, Halajian leg. (MMBC). — Ex Quelea quelea quelea (Linnaeus, 1758) (Ploceidae): 1♂, 1♀, North Cameroon, Marona, J.Mouchet leg. (NHML); 2♂, 2♀, Senegal, Matam (15°37′N 13°20′W), 6.ix.2007, I. Literak and M. Capek leg. (MMBC). — Ex Serinus canaria (Linnaeus, 1758)–captive bird (Fringillidae): 1♀, 1♂, New Zealand, Christchurch, 20.xii.1944, R.L.C. Pilgram Collection (MONZ). — Ex Spinus magellanicus (Fringillidae): 4♀, 2♂, 2 nymphs, Peru, Cascay, Huanuco (9°50’S 76°08’W), 20. and 22.viii.2011, I. Literak leg (MMBC: O. Sychra PE16–19). — Ex Sporophila nigricollis (Vieillot, 1823) (Thraupidae): 1♂, Peru, Cascay, Huanuco (9°50’S 76°08’W), 21.viii.2011, I. Literak leg (MMBC: O. Sychra PE20). — Ex Vidua macroura (Viduidae): 2♀, São Tomé and Príncipe, Missão Zoológica a São Tomé, loc. 41, São João dos Angolares (MZUL: 23/6/984).

Remarks

Piaget (1880) gave only a short description of M. quadrifasciata based on 13 females and 11 males from Passer domesticus. Later Thompson (1937) in his review of Piaget’s collection referred to the presence of only one slide with two females of M. quadrifasciata, but mentioned Passer montanus as host. He also stated: “A male is mentioned in the original description, but there is no male in the collection.” Subsequently Clay (1949b) specified that there is no original Piaget’s specimen of M. quadrifasciata from the type host, either in the NHML or in the museum in Leiden and confirmed the presence of two females from Passer montanus in the NHML.

We were able to examine slide no. 840 mentioned by Thompson (1937) and Clay (1949b), labeled as Menopon fasciatum, that is deposited in NHML and originally from Piaget’s collection. Moreover, there were also three slides labeled as “Myrsidea 4fasciata” from Passer domesticus in the collections of NHML; but in fact, there is actually only one slide (No. B.M.1955–616) with one male (here designated as neotype) belonging to this species. On the next two slides (both under the same number, B.M.1980-40) there are two females of Menacanthus eurysternus (Burmeister, 1838) collected from the same locality as Myrsidea, i. e. England: Cheshire, Great Budworth and Plumbey by A.W. Boyd (10.ix.1932), and J.S. Booth (8.10.1932), respectively. It is probably the same situation concerning the record of Menacanthus quadrifasciatum Piag. from house sparrow (collected by A.W. Boyd (13.3.1923) in Great Budworth) reported by Britten (1932). The name of this species is manually rewritten as Menacanthus spinosus Piaget, 1880 (now M. eurysternus) in the available copy of this paper on phthiraptera.info web page (http://phthiraptera.info/sites/phthiraptera.info/files/44361.pdf).

There are few reports about the occurrence of M. quadrifasciata on P. domesticus and P. montanus (see Table 1). It is quite prevalent in Asia with prevalence 20–50% and mean intensity only about 2 specimens per infested bird (Table 1).

Table 1.

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Summary of published records of examined sparrows and collected Myrsidea quadrifasciata quadrifasciata from Passer domesticus and Passer montanus within and out of their native range. –– Abbreviations: E=number of examined birds; P=number of parasitised birds; %=prevalence; MA=mean abundance; ?=not mentioned.

Host / Country	E	P	%	MA	Number of collected lice	Reference
Passer domesticus
Azerbaijan	514	21	4.1	0.078	40	Gadzhiev and Mustafaeva (1981)
Belarus	93	0	0	0	–	Zhuk and Nikalaeva (1987)
Bulgaria	118	1	0.8	0.008	1 ♀	Touleshkov (1974)
Czech Republic	436	1	0.2	0.002	1 ♂	Macháček (1977a)
Czech Republic	86	0	0	0	–	present study
England	473	0	0	0	–	Brown and Wilson (1975)
England	237	0	0	0	–	Thompson (1957)
India	100	20	20	?	Range 2–28 lice per bird	Saxena et al. (2007)
Iran	9	0	0	0	–	Moodi et al. (2013)
Pakistan	129	39	30.2	0.66	85	Naz et al. (2021)
Romania	492	0	0	0	–	Pap et al. (2013)
Turkey	22	0	0	0	–	Dik et al. (2013)
TOTAL (within native range)	2709	82	3.0	?
Canada, Manitoba	455	0	0	0	–	Galloway (pers. comm.)
Panama	58	0	0	0	–	Martin et al. (2007)
USA, Indiana	300	0	0	0	–	McGroarty and Dobson (1974)
USA, Kansas	567	0	0	0	–	Hoyle (1938)
USA, Kentucky	77	0	0	0	–	Wilson (1958)
USA, Massachusetts	34	0	0	0	–	Brown and Wilson (1975)
USA, New Hampshire	44	0	0	0	–	Keirans (1966)
USA, New Jersey	62	0	0	0	–	Martin et al. (2007)
USA, Oklahoma	127	0	0	0	–	Weddle (2000)
USA, Wisconsin	391	0	0	0	–	Woodmann and Dickie (1954)
TOTAL (out of native range)	1660	0	0	0
Passer montanus
Belarus	235	0	0	0	–	Zhuk and Nikalaeva (1987)
Czech Republic	433	2	0.5	0.021	2♂, 2♀, 5 nymphs	Macháček (1977a)
Czech Republic	15	2	13	0.133	1♂, 1♀	present study
Iran	8	0	0	0	–	Moodi et al. (2013)
Thailand	140	70	50	?	?	Boonkong and Meckvichai (1987)
TOTAL (within the native range)	831	74	9.0	?

Within the M. quadrifasciata complex, we found genetic divergences of 0.0–6.6% among the obtained sequences of COI from six Myrsidea samples examined in this study (Table 2, lines 1–3, 7–9). In comparison with GenBank, we found three other sequences with < 10% divergence (Myrsidea cf. textoris ex Ploceus ocularis; two Myrsidea sp. ex Vidua macroura), while the interspecific genetic distance from other species always exceeded 13%, the three closest species being M. cf. bubalornithis, M. seminuda and Myrsidea sp. ex Linurgus olivaceus (Table 2). Sequences for the EF-1α gene for all our examined Myrsidea specimens were identical, while sequences for all other species (with the exception of the Myrsidea sp. ex Vidua macroura) showed divergence over 5% (Table 2). Phylogenetic relationships among Myrsidea sequences obtained during this study and other Myrsidea sequences are presented in Fig. 21 and Fig. S1.

Figure 21. 

Phylogenetic tree of the Myrsidea species based on concatenated partial COI and EF-1α sequences. The tree was inferred using the maximum likelihood method based on the GTR+G+I model. The tree with the highest log likelihood is shown. Bootstrap support is shown next to the branches (values < 50% not shown). The tree is drawn to scale, with branch lengths in proportion to expected number of substitutions per site, as represented by the scale bar. Samples of M. quadrifasciata discussed in the present paper are in bold type. –– Colours: green – samples from Ethiopian Region; red – samples from Neotropical Region; blue – samples from Nearctic Region.

Principal Component Analysis (Fig. 22) using morphological data showed that there is no significant difference between the individuals of the different species in both males and females. Body size of 33 hosts was positively correlated with size of their Myrsidea (Table S1): bird size in centimetres (cm) vs. louse female TW: R=0.6703, P < 0.001; bird size in cm vs. louse female TL: R=0.4358, P < 0.01; bird body mass in grams (g) vs. louse female TW: R=0.7058, P < 0.001; bird body mass in g vs. louse female TL: R=0.5305, P < 0.01 (Fig. 23). Contrary to this, there is no correlation between host size and total number of louse female tergal setae (bird size in cm vs. louse female total number of tergal setae: R=0.2338, P=0.16; bird body mass in g vs. louse female total number of tergal setae: R=0.1486, P=0.38).

Figure 22. 

Principal Component Analyses (PCA) using 26 morphological traits of 43 males and 71 females. A: PC1 and PC2; B: PC1 and PC3. PC1 explains 44.36%, PC2 13.01% and PC3 9.37%.

Figure 23. 

Host-parasite body size correlation. Birds are characterized by the body size in centimetres and body mass in grams. Lice are characterized by the female temple width (TW) and total length (TL) (source data in Table S1).

Passer domesticus, the type host of M. quadrifasciata, is a widespread species. Its native range includes the Palearctic and Oriental Regions, but it was also introduced to the Nearctic and Neotropical Regions and the southern parts of the Afrotropical and Australasian Regions (Summers-Smith 2009). A total of six species of chewing lice were recorded on this host (Price et al. 2003) and according to our experience, M. quadrifasciata is the rarest and the least known species. There are only a few scarce reports about its occurrence (see Table 1), with no record out of its original range (Brown and Wilson 1975; Paterson et al. 1999; see also references in Table 1). The finding of a slide with M. quadrifasciata from Passer domesticus from Hawaii deposited in USNM (reported as Myrsidea sp. by Alicata et al. 1948) shows that this species was introduced out of its original range and that is why we can not exclude the possibility that it may also occur in other regions where its host has been introduced. It is interesting that all House Sparrows in Hawaii are believed to have descended from nine sparrows imported from New Zealand in 1871 (Caum 1933). But to date, no records of Myrsidea from this host have been reported from New Zealand (Paterson et al. 1999; Galloway 2005; Palma 2017), where House Sparrows were introduced from England sometime between 1862–1871 (Baker 1980). The hypothesis of its Palearctic-Oriental origin is supported by a slide with M. quadrifasciata from Passer domesticus from the USA (Mississippi, Tibbee) that is deposited in KCEM. On the other hand, the occurrence of Myrsidea from this species-complex on Agelaius phoeniceus from South Carolina deposited in USNM opens the possibility for the hypothesis that this species of Myrsidea may be common in the USA on icterid hosts and that Myrsidea on P. domesticus could be stragglers from these hosts.

Myrsidea quadrifasciata is prevalent in Asia with a prevalence 20–50% (Table 1). It is in accordance with Bush et al. (2009) who suggested that Myrsidea is probably adapted to more humid habitats, and thus, it is mainly present in the wetter subtropical and tropical areas (such as India and Thailand in our case). Scarce reports from Europe may be because the type host, P. domesticus probably spread spontaneously from Central and southern Asia to Europe thousands of years ago (Johnston and Klitz 1977; Šefrová and Laštůvka 2005). Probably thanks to that, some authors considered M. quadrifasciata as an alien species in Europe (Šefrová and Laštůvka 2005; Kenis and Roques 2010). We disagree with this idea. If P. domesticus spread to Europe thousands of years ago it can be already considered as native species. Moreover, as we are reporting here, M. quadrifasciata also occurs on P. montanus that is native in Europe (Summers-Smith 2009).

“Myrsidea anoxanthi”. Price and Dalgleish (2007) placed M. anoxanthi into the “serini species group” and mentioned the following differences between this species and M. serini: 1) “Both sexes of M. anoxanthi are consistently smaller than those of M. serini, generally being at or below the lowest values of the ranges given by Klockenhoff (1984a)”; 2) “the females tend to have fewer abdominal setae, especially on the anterior tergites and sternites”; 3) “Males are not as clearly separated by these quantitative data, but the metanotal margin of M. anoxanthi has only 10 setae versus 11–15 for M. serini.” (according to the setal counting system used in this paper, the last sentence should be changed as: M. anoxanthi has only 8 setae versus 9–13 for M. serini, see Table S3). In their remarks, Price and Dalgleish (2007) stated: „These two species are clearly closely related, but the new species quantitatively is sufficiently distinct to justify its recognition.“ When we compared morphometric characteristics of these species according to their original descriptions and all examined specimens, we can definitively say that there are no significant differences either in number of abdominal setae of female or metanotal marginal setae of male (see Tables S3, S4). Thus, the remaining differences between these two species are only in their dimensions (Tables S11, S12). It is also true for males collected from Sporophila nigricollis (a bird species related to known host of “M. anoxanthi”, Sporophila minuta) that is at or below the lowest values of the ranges of “M. anoxanthi” given by Price and Dalgleish (2007). We believe that this difference can be affected by host size, because seedeaters of the genus Sporophila are the smallest hosts of M. quadrifasciata (Table S1). Harrison’s Rule supports that smaller hosts harbour smaller lice (Johnson et al. 2005; Harnos et al. 2016). According to these data, we believe that M. anoxanthi is conspecific with M. quadrifasciata. Therefore, we place M. anoxanthi as a junior synonym of M. quadrifasciata.

“Myrsidea argentina”. Myrsidea argentina was described by Kellogg (1906) on the basis of a single specimen, supposedly a female, from Argentina. On the basis of Kellogg’s figure and description, Cicchino and Valim (2015) discussed morphological relationships between M. argentina and M. serini. They supported the note by Clay (1968) that Kellogg’s specimen was most likely a third instar nymph, not a female (Cicchino and Valim 2015). After comparison of morphometric characteristics of our specimens with the description of M. serini by Cicchino and Valim (2015), we suggest that M. argentina is most likely conspecific with M. serini. As we synonymize M. serini with M. quadrifasciata (see below), we also place M. argentina as a junior synonym of latter species.

“Myrsidea balati”. Myrsidea balati was described on the basis of two males and two females found on two of 434 examined Passer montanus by Macháček (1977a), who was able to compare them with one male of Myrsidea quadrifasciata that he found on one of 436 examined Passer domesticus in the Czech Republic. Unfortunately, the slides with holotype male (No. 2–320a) and allotype female (No. 2–320c) are probably lost (Vladimir Jansky, Slovak National Museum, Bratislava, Slovakia, pers. comm. 2017). There is only the second and last paratype male available in the collection of ZFMK.

Contrary to ischnoceran lice, where Macháček (1977b) correctly suggested that both species of sparrows share the same species of lice, Brueelia cyclothorax (Burmeister, 1838), Philopterus fringillae (Scopoli, 1772) and Sturnidoecus ruficeps (Nitzsch, 1866), in the case of Myrsidea, unfortunately he was wrong. As main diagnostic characteristics of M. balati, he used the ratio of lengths of setae in asters, head ratio and total length, and he compared only three males. When we compared our examined specimens, we found that all aforementioned characteristics of Myrsidea from both species of sparrows overlap. Since all other characters are almost identical (Tables S3–S12), we place M. balati as a junior synonym of M. quadrifasciata. It is also in accordance with Touleshkov (1962), who mentioned M. quadrifasciata from Passer montanus from Bulgaria.

“Myrsidea darwini”. Palma and Price (2010) placed M. darwini into the “serini species group” and mentioned that it can be separated from the three species in that group (M. anoxanthi, M. major and M. serini) by 1) having “fewer metanotal and abdominal setae”; 2) “the relative length of the postspiracular setae”; and 3) “details of the male genital sac sclerite: compare fig. 3 (in Palma and Price 2010) with fig. 2B in Klockenhoff (1984a) for Myrsidea serini (Seguy, 1944), and fig. 44 in Price and Dalgleish (2007) for Myrsidea anoxanthi Price and Dalgleish, 2007.”

When we compared morphometric characteristics of these species according to their original descriptions and all examined specimens, there are no more significant differences either in number of abdominal setae of both sexes or in the relative length of the postspiracular setae (see Tables S3–S12). Slight differences of the male genital sac sclerites mentioned by Palma and Price (2010) may be caused by distortion of this tiny structure. When we compare drawings of male genital sac sclerites in the original descriptions or redescriptions, we can see variability in their shape even in the case of different males from the same host (Figs 4–18). The best example of this is a male from Agelaoides badius from Paraguay (Fig. 8), where we can see differences even between the left and right sides of the single sclerite. Therefore, the only unique character is the small number of metanotal setae of the male (Table S4) and slight differences in dimensions (Table S12). According to these data we believe that M. darwini is conspecific with M. quadrifasciata. Therefore, we place M. darwini as a junior synonym of M. quadrifasciata.

“Myrsidea major”. Piaget (1880) gave only a short description of this species based on 16 females and 13 males. Later Thompson (1937), in his review of Piaget’s collection, referred to the presence of only two slides with five males of M. quadrifasciata var. major. He also stated: „Females are mentioned in the original description, but there are no females in the collection.” Contrary to this, Clay (1949a) indicated that there are two slides (No. 841 and 842) with six females. She also designated the female on slide 842 as the lectotype and other females as paratypes. All six females were examined by Price and Dalgleish (2007). These authors stated that this species is: “morphologically closest to M. serini, differing principally in having longer postspiracular setae on tergites V–VII, somewhat greater total length, and fewer setae on tergite VII. While these differences are not profound, we have opted to continue to recognize this as a valid species pending additional collections from the type host and the study of male specimens.” When we compared characteristics of M. major by Price and Dalgleish (2007) with our examined specimens of M. quadrifasciata, we found that all aforementioned characteristics overlap. Since all other characters are almost identical (Tables S3–S11), we place M. major as a junior synonym of M. quadrifasciata.

“Myrsidea queleae”. This species was described by Tendeiro (1964) from Quelea quelea from the family Ploceidae from South Africa. Later it was redescribed by Klockenhoff (1984b), who also provided statistical evaluation of populations of “M. queleae”, “M. serini” and “M. textoris” (see discussion about subspecies concept below).

“Myrsidea serini”. This species was described by Séguy (1944) from Serinus serinus from the family Fringillidae from France. Later, it was redescribed by Klockenhoff (1984a), Price and Dalgleish (2007), and Cicchino and Valim (2015). Descriptions and illustrations of both sexes presented by these authors are almost completely consistent with that of M. quadrifasciata (Tables S3–S12), so we place M. serini as a junior synonym of this species. As stated by Price and Dalgleish (2007) and Cicchino and Valim (2015) “M. serini” represents: “atypical species, considering the host distribution patterns presented in Myrsidea genus, due to its occurrence” on eight bird species from families Emberizidae, Fringillidae and Icteridae. Since the only practical manner to deal with the taxonomy of such a large genus as Myrsidea was, and still is, to treat lice from each host family as a unit, it is easy to overlook similarity of Myrsidea parasitizing hosts from different families and regions. We expect that a more complex review of the genus will reveal more similar cases.

“Myrsidea textoris”. This species was described by Klockenhoff (1984b) from Ploceus cucullatus from the family Ploceidae from Ghana. Klockenhoff (1984b) also provided statistical evaluation of populations of “M. queleae”, “M. serini” and “M. textoris” (see discussion about subspecies concept below).

“Myrsidea viduae”. This species was described on the basis of only two females found on Vidua macroura from Sao Tomé e Principe by Tendeiro (1993). Since all characters are almost identical with those of M. quadrifasciata (Tables S3–S11), and we found also low genetic differentiation, we place M. viduae as a junior synonym of M. quadrifasciata.

Myrsidea from Microspingus melanoleucus. We found only one female of Myrsidea on this host in Paraguay (see material examined). At the same day when we collected this female on Microspingus melanoleucus (bird no. PG359), we also examined one Agelaoides badius (bird no. PG357) with a few Myrsidea (reported as “M. serini” by Kolencik et al. 2016). Therefore, it is most likely that this is the result of contamination while collecting. On the other hand, we can not completely exclude that this case represents an example of natural host-switching because as we have shown, M. quadrifasciata also occurs on birds from the family Thraupidae. As shown by Weckstein (2004) or Kounek et al. (2011), host-switching between different host species is possible at one location between birds with similar behaviour and ecology.

Klockenhoff (1984b) provided statistical evaluation of populations of “M. queleae”, “M. serini” and “M. textoris”. He found significant differences between these populations and he supposed that these differences show interspecific rather than intraspecific variation. Thus, he considered these taxa separate species. When we compared our material of “M. queleae” with Klockenhoff’s data, we found only few differences in setal counts on both sexes (Tables S13, S14). Since we have material from the same host species as Klockenhoff (Quelea cardinalis and Q. quelea), we believe these differences are related to intraspecific morphological variability in the species. Unfortunately, Klockenhoff (1984b) did not provide statistical data for measurements of this species, so we could not evaluate them. Similarly, differences in some setal counts for our specimens of “M. textoris” can, by our opinion, be attributed to intraspecific variation. Beside the type host (Ploceus cucullatus), we examined Myrsidea from five other Afrotropical ploceids (Euplectes franciscanus, E. jacksoni, E. progne, Ploceus madagascariensis and P. nigricollis) and one Asian species (Ploceus philippinus). Different sizes of these hosts correlated with different sizes of their Myrsidea (Fig. 23, Table S1). This observation, known as as Harrison’s Rule, is well known within chewing lice and has been documented also in a wide variety of other parasitic organisms (Harnos et al. 2016). This biological rule can also explain the observed differences in measurements of our and Klockenhoff’s material. Contrary to “M. queleae” and “M. textoris”, we found more significant differences between our samples of “M. serini” from Neotropical hosts and data provided by Klockenhoff (1984b) for “M. serini” from hosts from the Palearctic Region. Similarly, when we compared characteristics of M. quadrifasciata from Passer domesticus and P. montanus, we found significant differences between specimens of Myrsidea from these hosts and specimens from all aforementioned taxa. Recorded differences show the following pattern:

In cases where there is a larger number of examined females, such as for M. quadrifasciata from Passer montanus (n=11) or “M. serini” reported by Klockenhoff (1984a) (n=35), we can find higher variability in the number of metanotal setae, 8–13 and 7–13, respectively (Table S3). We can see the same pattern in the case of males of “M. serini” (n=25), where Klockenhoff (1984a) reported 9–13 metanotal setae. One exception is “M. darwini” from Galápagos Islands with uniformly only 6 metanotal setae in both sexes (n=22 females and 7 males). In general, in the case of “M. darwini”, there is also a tendency to a smaller number of setae on tergites. Together with “M. anoxanthi” from the Neotropics and “M. viduae” from Africa, it lies at the lower limit of the range of tergal setae (Tables S3 and S4), and this is true for both sexes (the exception is “M. viduae” where only females are known, and for “Myrsidea cf. anoxanthi” from Sporophila nigricollis, where only one male is known).

On the other hand, there are “M. serini” from Agelasticus thilius petersii from Argentina and “M. queleae” from Africa with their numbers of tergal setae at the upper limit of the range (Tables S3 and S4). Moreover, females of “M. serini” from Agelasticus thilius petersii differ from all examined specimens by 8 setae on tergite VIII (vs. 3–6 setae; Table S3). Due to this fact, we have doubts as to whether these individuals really represent the species under consideration. More specimens from this host are needed to resolve this problem.

In the case of males, the highest numbers of tergal setae are recorded mainly on males of “M. queleae” and “M. textoris” from Africa. The most conspicuous differences are visible on tergite VIII: while specimens from Neotropical (“M. anoxanthi”, “M. darwini” and “M. serini”) and Palearctic (“M. balati” and “M. quadrifasciata”) have 4–8 setae (one exception is again “M. serini” from Agelasticus thilius petersii with 11 setae), specimens from Africa (“M. queleae” and “M. textoris”) have 8–14 setae (Table S4). Conversely, “M. serini” from Palearctic shows wide range of number of setae (6–12 setae) that overlap range of setae found on both aforementioned examples. Unfortunately, Klockenhoff (1984a) did not mention characteristics separately for particular hosts, so it is necessary to re-examine his material and re-evaluate these parameters according to hosts.

When we compare sternal chaetotaxy, we see a similar pattern as for tergites: 1) Neotropical specimens lie at the lower limit of the range of these setae; 2) African specimens, in this case including specimens from sparrows (“M. balati” and “M. quadrifasciata”), lie at the upper limit of the range of these setae; and 3) cases where there are larger numbers of examined specimens, i.e. “M. serini” reported by Klockenhoff (1984a) (n=35), and “M. textoris” reported by Klockenhoff (1984b) (n=28), which show high variability over almost the entire range of recorded values. So what is missing for other taxa above is a large range of specimens, which will likely support highly variable morphology in terms of number of setae.

Postspiracular setae show the same pattern in their ratio of lengths, with high variability in the lengths of these setae on a particular segment. In general, there are long to extremely long postspiracular setae on II, IV, VII and VIII and shorter with variable length setae on I, and shortest on III, V and VI (Tables S9 and S10).

Concerning different body sizes, in general, “M. anoxanthi” and “M. viduae” are represented by the smallest individuals (for example, TW of females 0.34–0.37 and TW of males 0.33–0.34), while Myrsidea from the Icteridae are represented by the largest ones (for example TW of females 0.44–0.46 and TW of males 0.40–0.42). Similarly, as in the case of setal counts, “M. serini” reported by Klockenhoff (1984a) for 35 individuals from five hosts of different size show the highest variability in measurements with values overlapping both of the mentioned limits (for example TW of females 0.36–0.43 and TW of males 0.34–0.39) (Tables S11, S12). Contrary to these data, there is no correlation between host size and total number of tergal setae in females.

Observing the PCA plots for PC1 and PC2 and the PC1 and PC3 revealed the overlapping of all examined groups of Myrsidea, supporting that all analysed individuals of M. quadrifasciata complex form one morphological group with a few outliers.

Taking into consideration all these parameters, host associations and geographic distribution, we suggest that the only way to deal with these taxa is to follow the concept of subspecies. Palma and Price (2010) applied it to two morphologically distinct populations of Myrsidea nesomimi from the Galápagos Islands, which were later confirmed by genetic data by Štefka et al. (2011). Štefka et al. (2011) reported that M. nesomimi from one locality or from a few close ones showed minimal genetic differences (0.1–0.6%), while lice of the two subspecies from different hosts and distant localities showed increasing genetic variability (4.5–5.1%). Our molecular data support these subspecies concepts, since we found divergences of 0.0–6.6% among the newly obtained sequences of COI from six Myrsidea samples examined in this study (Table 2: lines 1–3, 7–9), and up to 9.3% inside the whole proposed M. quadrifasciata complex (Table 2), while the interspecific genetic distance from other species always exceeded 13%. Even species collected from other birds belonging to families in which lice from the M. quadrifasciata complex occur (e.g., Ploceidae) ranged over 20% in distance (Table 2). It is also in accordance with Kolencik et al. (2017), who proposed a limit of interspecific genetic diversity at 12% divergence. Similarly, concerning the EF-1α gene, all our examined Myrsidea sequences were identical and the divergence within the proposed species did not exceed 0.3% (Table 2), while sequences for other species showed divergence over 5%. We propose these low divergences are a limit of interspecific genetic diversity in this gene.

Because for most Myrsidea species, only a relatively short sequence of the COI gene is available, all conclusions inferred from the phylogenetic analyses are necessarily limited; no deeper phylogenetic conclusions can be reached and we can not speculate about the definitive position of the M. quadrifasciata complex in context of the genus Myrsidea. This necessary caution is further supported by relatively low bootstrap supports in the majority of tree branches (see Figs 21, S1). Nevertheless, it is true for both trees that our M. quadrifasciata sequences always group together, which supports the hypothesis of species identity of the proposed M. quadrifasciata complex.

Klockenhoff (1984b) discussed relationships between species from the “serini species group” (namely “M. queleae”, “M. serini” and “M. textoris”) and three other species of Myrsidea from hosts from the family Ploceidae (M. bubalornithis Klockenhoff, 1984, M. eisentrauti Klockenhoff, 1982 and M. ledgeri Klockenhoff, 1984). Our results corroborate with Klockenhoff’s (1984b) opinion that none of them belonged to the “serini species group”, i.e., the M. quadrifasciata complex presented in this study. While M. eisentrauti and M. ledgeri have a completely different type of male genital sac sclerite compared with M. quadrifasciata, M. bubalornithis share the same one. Despite this morphological similarity, the net average p-distances between M. bubalornithis and M. quadrifasciata are 14.3–16.9%. This genetic divergence allows us to exclude this species from the M. quadrifasciata complex.

The subspecies concept we are using here is accepted for other chewing lice, for example lice from the genera Gyropus (Gyropidae), Actornithophilus, Dennyus, Menacanthus (Menoponidae), Lunaceps, Saemundssonia (Philopteridae), Geomydoecus, Procaviphilus (Trichodectidae) (Price et al. 2003; Mey 2004). Our results also demonstrate the importance of geography in multi-host, polyxenous parasites. We suggest that overlapping distribution (sympatry) and the same habitat preferences (syntopy) of the hosts seem to be the most important factors maintaining genetic connectivity within geographic areas, because they provide a good opportunity for host-switching that can lead to establishment of naturally occurring populations of the same louse species on two or more distantly related hosts.

We propose the following subspecies (a list of their hosts and their geographic distributions is given in Table 3):

Palearctic Region:

M. q. quadrifasciata (Piaget, 1880) comb. nov.

M. q. serini (Séguy, 1944) comb. nov.

Paleotropic Region:

M. q. queleae Tendeiro, 1964 comb. nov.

M. q. textoris Klockenhoff, 1984 comb. nov.

M. q. viduae Tendeiro, 1993 comb. nov.

Neotropical Region:

M. q. anoxanthi Price and Dalgleish, 2007 comb. nov.

M. q. argentina (Kellogg, 1906) comb. nov.

M. q. darwini Palma and Price, 2010 comb. nov.